Intermolecular Forces and Solutions

Question 1

Definition of intermolecular forces

Answer 1

force of attraction that occurs between atoms, molecules, and ions due to their proximity in space to each other

Question 2

What’s stronger - intermolecular or intramolecular forces?

Answer 2

INTRAmolecular are stronger

Question 3

What affects the strength of attraction?

Answer 3

• Magnitude of charge (real or partial)
• distance between species

Question 4

The stronger the attractive forces between the particles , the more they -

Answer 4

resist moving or breaking apart

Question 5

What is polarity?

Answer 5

The separation of electrical charge along a bond due to differences in the electronegativity of the bonded atoms

Question 6

What leads to the formation of partial charges? (negative or positive)

Answer 6

Electron density not being equally shared between the two atoms

Question 7

What is surface tension?

Answer 7

A liquid’s resistance to increase its surface area
- the stronger the intermolecular forces, the more energy required to increase the surface area

Question 8

How does a liquid minimize surface area?

Answer 8

it forms spherical drops

Question 9

What is capillary action?

Answer 9

the spontaneous rising of a liquid in a narrow tube or the movement of a liquid up a piece of paper against the pull of gravity
- the result of cohesive and adhesive forces

Question 10

What is viscosity?

Answer 10

The measure of a liquid’s resistance to flow
- the amount of energy necessary to move an object through a fluid
- molecule size plays an important role

Question 11

What are some applications of intermolecular forces?

Answer 11

• Surface tension
• Capillary action
• Viscosity
• Receptor-Drug binding
• Phase changes
• Solubility

Question 12

What properties are determined by receptor-drug binding?

Answer 12

Efficacy, potency, and toxicity

Question 13

What does phase changes represent?

Answer 13

Changes in the phase of a substance with respect to temperature and pressure
- energy is required to disrupt molecular interactions and thus leads to changes in the states of matter

Question 14

What does solubility depend on?

Answer 14

Attractive forces of the solute and solvent
- substances with similar polarity will be soluble or miscible
- “like dissolves like”

Question 15

What is the weakest intermolecular force?

Answer 15

Van der Waals forces

Question 16

What is a Van der Waals force?

Answer 16

Interaction arising from the formation of induced dipoles between two non-polar molecules (or portions of molecules)

Question 17

What are dipole-dipole interactions?

Answer 17

• occurs in all polar molecules
• relatively strong interaction, but depends on the nature of the individual dipoles involved

Question 18

Hydrogen bonding

Answer 18

Very strong specialized dipole-dipole interaction
- H bond donor and H bond acceptor

Question 19

Ion-dipole

Answer 19

Very strong interaction between a full formal charge and a dipole
- depends somewhat on the strength of the dipole

Question 20

Electrostatic interactions

Answer 20

• ionic interactions between a cationic portion and anionic portion
• effective at distances farther than other types of interactions
• persist longer than other interactions

Question 21

Which intermolecular force is the strongest?

Answer 21

Covalent bonds

Question 22

What is a solution?

Answer 22

homogenous mixture of two or more substances

Question 23

What is a solvent?

Answer 23

Major component of the mixture (usually water)

Question 24

What is a solute?

Answer 24

the minority component of the mixture

Question 25

What does an aqueous solution mean?

Answer 25

the solvent is water

Question 26

What determines the solubility of one substance in another?

Answer 26

• intermolecular forces (like dissolves like)
• tendency to mix

Question 27

What does it mean if a compound is more water soluble?

Answer 27

it has more polar bonds

Question 28

What does a saturated solution mean?

Answer 28

a solvent is holding the maximum amount of solute dissolved
- even if you add more, it won’t dissolve

Question 29

What does an unsaturated solution mean?

Answer 29

a solution where the solvent holds less than the maximum amount of solute dissolved
- more solute will dissolve if added

Question 30

What does it mean if a solution is supersaturated?

Answer 30

The solvent holds more than the maximum amount of solute dissolved
- usually unstable
-

Question 31

How to calculate molecular weight -

Answer 31

add the sum of each atoms and how many there are

Question 32

How to calculate moles -

Answer 32

Mass of sample(g) /molecular weight (g/mol)

Question 33

How to calculate density -

Answer 33

Mass of sample (g)/ Volume of sample (mL)

Question 34

How to calculate Molarity (M)

Answer 34

moles of solute (mol) / L of solution

Question 35

Weight percent

Answer 35

a percentage of the solute mass in the mass of the solution
- assume a 100g sample
- percent becomes mass (g) / 100g

Question 36

Volume percent

Answer 36

solution concentration expressed as a percentage of the solute volume in the volume of the solution
- assume a 100 ml sample
- percent becomes volume (ml) / 100 mL